With all the blood and gore – and fantastically poetic staging care of director John Tiffany and choreographer Steven Hoggett – Morse code may not be the first thing you associate with the National Theatre of Scotland’s production of vampire Let the Right One, now playing at the West End’s Apollo Theatre. But it nevertheless plays a key role in the love story between lonely lad Oskar and his mysteriously pale paramour Eli, whose bedroom in the neighbouring house adjoins his.

Martin Quinn and Rebecca Benson in Let the Right One In

Oskar’s father educated him in Morse Code, and Oskar gives Eli a crash course so that the two can communicate through the partition wall at night. (What they communicate would be telling – go see the play.)

That snapshot got me curious about Morse Code. Maybe I could learn it as part of this month’s challenge? Uh, that would be a big fat NO. When I looked into it, I discovered that it takes the average student a minimum of two to three months to reach a speed of a measly 20 wpm. A monkey could send a text message faster.

And what’s more, unless you’re a ham radio geek (I mean, enthusiast), there’s little point. While Morse Code, which was developed in 1844, was instrumental in the early days of radio communication before it was possible to transmit voice, over the mid- to late- twentieth century, it was gradually phased out of military, aviation and, finally, maritime use as technology overtook it. In the last case, it was the standard communication for maritime distress for 96 years until 1999, when it was replaced by the ship-to-shore Global Maritime Distress Safety System (think Tom Hanks in Captain Phillips).

So I didn’t learn Morse Code but the most fascinating thing I learned about Morse Code is this: SOS doesn’t mean anything. Many people assume SOS, universally recognised as a life-threatening, disaster-imminent cry for help, is an acronym, perhaps standing for “save our ship” or “save our souls”. But that’s not the case at all.

Three dots, three dashes, three dots

To explain, I do need you to know a little more about Morse code. It’s a language in which each letter and number is represented by a unique sequence of dots and dashes, or dits and dahs in Morse-speak, of a certain duration. When transmitting, a dash is three times the duration of a dot. Every dot or dash is followed by a brief silence, every letter-sequence in a word is followed by a silence equal to three dots (or one dash), and every complete word is followed by a silence equal to seven dots. (Throw in a few paragraph breaks and that 20 wpm is starting to make sense, right?)

For emergency signals, Morse uses what’s called prosigns, sequences that don’t represent text but can be keyed quickly, run together – foregoing any separating silences – and easily remembered. The most common distress signal is three dots followed by three dashes followed by three dots (as shown above). Which just happens to correspond with the letter sequences for S-O-S.

Another trivia titbit for you: Titanic was one of the first commercial oceanliners to use SOS. It had been signed into effect by international treaty in 1908 – the signal to be repeated at short intervals – but in practice, it was slow to be adopted, particularly as many British sailors had been trained in the competing Marconi system rather than Morse code (invented by Americans). On Titanic, the radiographer, presumably unsure on that perilous night in 1912 who was listening to what, interspersed the two. The sinking of the Titanic provided the catalyst for rapid, widespread use and monitoring of SOS distress signals.

Titanic’s sinking accelerated the adoption of SOS

While no longer employed in regular professional radio communications, SOS does live on as a visual signal for distress for those instances when you’re stranded on desert island with no wifi access (think Tom Hanks, again, but this time in Castaway).

And while the letters still don’t mean anything in terms of a cry for help, there are plenty of uses of SOS that are bona fide acroynms. Check out this extensive list on acronymfinder.com – a fantastically useful website, by the way – where you can find options from Secretary of State and Same Old Story to Statement of Sensitivity, Source of Strength, Smash on Sight, Spawn of Satan, and my personal favourite, Save Our Saucepans.

Since 1996, I have been passionate about promoting UK theatre, not least through WhatsOnStage.com and the WhatsOnStage Awards, which I founded, and my latest theatre websites, StageFaves.com, a pioneering social media directory for musicals, and MyTheatreMates.com, a portal for theatre bloggers I co-founded with Mark Shenton. In addition, I have hosted hundreds of post-show Q&As, panel debates and other talks with all types of theatremakers. I have also written for various publications including The Times, Evening Standard, Express and Daily Telegraph, and have commented on theatre in a wide variety of print, digital, and broadcast media. Apart from my love of theatre, I am the author of two published novels, Come Clean and Beware the Dwarfs. Follow me on Twitter @TerriPaddock.